Polyetherketoneketone (PEKK) has been melt spun into fibers which have potential in the areas of filtration, protective clothing apparel and commercial furnishings. Unfortunately these fibers are difficult to dye under usual textile dyeing conditions since the fibers contain no active dye sites. Conditions normally employed for dyeing polyester have been tried on PEKK fibers (i.e., thermosol dyeing using disperse dyestuffs) with limited success. The present invention not only offers a novel technique for dyeing PEKK fibers, but this technique also stabilizes the fiber to shrinkage.